Spiny leaf gall wasp has laid eggs on this wild rose, which caused the plant to produce these spiny galls.

Spiny-Leaf-Gall Wasp (Diplolepis polita) is in the Rose Gall Wasps (Diplolepidinae) Subfamily.

Plant Galls of the Western United States, pp. 297-298, fig. 81, plate 517.

Gallformers: https://www.gallformers.org/gall/1476

BugGuide: https://bugguide.net/index.php?q=search&keys=Diplolepis+polita

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What is a Gall? Gallformers: https://www.gallformers.org/
"Plant galls are abnormal growths of plant tissues, similar to tumors or warts in animals, that have an external cause--such as an insect, mite, nematode, virus, fungus, bacterium, or even another plant species. Growths caused by genetic mutations are not galls. Nor are lerps and other constructions on a plant that do not contain plant tissue. Plant galls are often complex structures that allow the insect or mite that caused the gall to be identified even if that insect or mite is not visible."

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GALLS (annotated references)

Plant Galls of the Western United States: a photographic guide to 536 species of plant galls found west of the Rockies, with 400+ color images and plates, Ronald A. Russo, April 2021. (Available on Amazon)

Gallformers: Identify Galls by name or by host plant https://www.gallformers.org/id

INaturalist Project, Galls of California https://www.inaturalist.org/projects/galls-of-california

California Oak Galls (photo guide), Joyce Gross: https://joycegross.com/galls_ca_oak.php
California Oak Galls Induced by Unknown or Undescribed Species (photo guide), Joyce Gross: https://joycegross.com/galls_ca_oak_undescribed.php
Nancy Asquith Journal: California Oak Galls https://www.inaturalist.org/projects/california-plants-with-mystery-galls/journal/44142-california-oak-galls
Nancy Asquith Journal: https://www.inaturalist.org/projects/galls-of-california/journal/44203-where-to-learn-more-about-galls
BugGuide: Identification, Images, & Information for insects and other gall-inducers, (US & Canada) clickable categories or use search bar: https://bugguide.net/node/view/3/bgpage
BugGuide: Unidentified Tracks, Larvae, Webs, Parasites, and Other Mysteries: https://bugguide.net/node/view/696662/bgpage
INaturalist Project: https://www.inaturalist.org/projects/all-your-galls-are-belong-to-us

I found this gall on the underside of a Coast Live Oak leaf under the host tree. I believe it's a Two-horned Gall. There were a few present in the leaflitter.

Host plant: https://www.inaturalist.org/observations/208189611

These photos were edited to have a Custom White Balance in Photoshop (Photoshop's preset).
Photo 3 was brightened.

I found this gall on the underside of a Coast Live Oak leaf under the host tree. I believe it's a Two-horned Gall. There were a few present in the leaflitter. It has 1 exit hole.

Host plant: https://www.inaturalist.org/observations/208189611

These photos were edited to have a Custom White Balance in Photoshop (Photoshop's preset).
Photos 1 and 3 were brightened.

I found this Live Oak Bud Gall in the leaflitter under a Coast Live Oak tree. It has 1 old exit hole. I bisected the gall.

Host plant: https://www.inaturalist.org/observations/208189611

Photos 1-5 and 7-9 were edited to have a Custom White Balance in Photoshop (Photoshop's preset).
Photos 1-3, 5, and 7-8 were brightened.
Photo 6 was not edited.

I found this Live Oak Bud Gall in the leaflitter 10 feet away from a grove of Coast Live Oaks. The gall has a dimple on each end and an exit hole.

The Coast Live Oak grove is uphill and I've observed as many of the trees as I can at the following link: https://www.inaturalist.org/observations?nelat=33.82086229210912&nelng=-117.77517934718838&place_id=any&subview=map&swlat=33.8204701050261&swlng=-117.77633806148282&taxon_id=47851&verifiable=any

I found this Live Oak Bud Gall in the leaflitter 10 feet away from a grove of Coast Live Oaks. The gall has a dimple on each end and no exit holes. The Coast Live Oak grove is uphill and I've observed as many of the trees as I can at the following link:

Here are the potential host trees on the hill above the gall (mostly Coast Live Oaks): https://www.inaturalist.org/observations?nelat=33.82086229210912&nelng=-117.77517934718838&place_id=any&subview=map&swlat=33.8204701050261&swlng=-117.77633806148282&taxon_id=47851&verifiable=any

There were a lot of Live Oak Bud Galls surrounding it which had exit holes. Location corrected.

? not sure if beginning of galls

https://www.inaturalist.org/taxa/768494-Aphis-origani?

galls https://www.inaturalist.org/observations/214583226, ant https://www.inaturalist.org/observations/214583227